The need to take liquid samples from depths within a body of such liquids occurs in a number of contexts. For example, it is often necessary to withdraw a sample of oil from a known depth within an oil storage tank, so as to analyse its composition. Similarly, in checking on water quality in inland lakes and streams, analysis of water samples from known depths may be required. Also in industrial waste disposal processes which require the use of settling tanks and ponds, monitoring of progress of the process requires the extraction of liquid samples from known depths. There is thus a need for an apparatus which is simple yet efficient in use, for collection of such samples.
The lowering of a simple container to the required depth and collection of liquid therein is the simplest means, provided that one can be sure that all of the liquid collected therein comes from the required depth. In order to accomplish this, the container should preferably remain closed until the predetermined depth is reached, and then opened at that depth for filling purposes. Then it must be withdrawn to the surface without spillage and refilling thereof with liquid from another depth level. It is also desirable to be able to collect a sample of known, predetermined size in a convenient form of container for subsequent laboratory analysis.